Biophysics and medical effects of enhanced radiation weapons

Where are the medical countermeasures against the ARS and DEARE? A current topic relative to an animal model research platform, radiation exposure context, the acute and delayed effects of acute exposure, and the FDA animal rule

PURPOSE

A question echoed by the National Biodefense Science Board (NBSB) in 2010, remains a reasonable question in 2023; 'Where are the Countermeasures?'. A critical path for development of medical countermeasures (MCM) against acute, radiation-induced organ-specific injury within the acute radiation syndrome (ARS) and the delayed effects of acute radiation exposure (DEARE) requires the recognition of problems and solutions inherent in the path to FDA approval under the Animal Rule. Keep Rule number one in mind, It's not easy.

CONSIDERATIONS

The current topic herein is focused on defining the nonhuman primate model(s) for efficient MCM development relative to consideration of prompt and delayed exposure in the context of the nuclear scenario. The rhesus macaque is a predictive model for human exposure of partial-body irradiation with marginal bone marrow sparing that allows definition of the multiple organ injury in the acute radiation syndrome (ARS) and the delayed effects of acute radiation exposure (DEARE). The continued definition of natural history is required to delineate an associative or causal interaction within the concurrent multi-organ injury characteristic of the ARS and DEARE. A more efficient development of organ specific MCM for both pre-exposure and post-exposure prophylaxis to include acute radiation-induced combined injury requires closing critical gaps in knowledge and urgent support to rectify the national shortage of nonhuman primates. The rhesus macaque is a validated, predictive model of the human response to prompt and delayed radiation exposure, medical management and MCM treatment. A rational approach to further development of the cynomolgus macaque as a comparable model is urgently required for continued development of MCM for FDA approval.

CONCLUSION

It is imperative to examine the key variables relative to animal model development and validation, The pharmacokinetics, pharmacodynamics and exposure profiles, of candidate MCM relative to route, administration schedule and optimal efficacy define the fully effective dose. The conduct of adequate and well-controlled pivotal efficacy studies as well as safety and toxicity studies support approval under the FDA Animal Rule and label definition for human use.

Nuclear and Radiological Emergencies: Biological Effects, Countermeasures and Biodosimetry

Atomic and radiological crises can be caused by accidents, military activities, terrorist assaults involving atomic installations, the explosion of nuclear devices, or the utilization of concealed radiation exposure devices. Direct damage is caused when radiation interacts directly with cellular components. Indirect effects are mainly caused by the generation of reactive oxygen species due to radiolysis of water molecules. Acute and persistent oxidative stress associates to radiation-induced biological damages. Biological impacts of atomic radiation exposure can be deterministic (in a period range a posteriori of the event and because of destructive tissue/organ harm) or stochastic (irregular, for example cell mutation related pathologies and heritable infections). Potential countermeasures according to a specific scenario require considering basic issues, e.g., the type of radiation, people directly affected and first responders, range of doses received and whether the exposure or contamination has affected the total body or is partial. This review focuses on available medical countermeasures (radioprotectors, radiomitigators, radionuclide scavengers), biodosimetry (biological and biophysical techniques that can be quantitatively correlated with the magnitude of the radiation dose received), and strategies to implement the response to an accidental radiation exposure. In the case of large-scale atomic or radiological events, the most ideal choice for triage, dose assessment and victim classification, is the utilization of global biodosimetry networks, in combination with the automation of strategies based on modular platforms.

Prognostic assessment of the zone of occurrence of radiation combined injuries within a nuclear blast area

BACKGROUND

A detonation of nuclear weapon (NW) is considered as one of the most devastating radiological scenarios in the list of modern global threats. An essential proportion of victims in a mass casualty radiation event may require an immediate medical care due to radiation combined injuries (RCI). Surprisingly, there is a lack of clear guidance for quantitative prognosis of the spatial distribution of expected RCI casesin a given nuclear explosion scenario.

PURPOSE

This work is aimed at the presentation of a new, improved model, allowing more confident evaluation of the contributions from different NW destructive forces to RCI formation, thus leading to more accurate approximation of the zone around the epicenter for a guided search for RCI cases.

MATERIALS AND METHODS

The model is made compatible with a classic approach and provides the estimates of radial distance from the epicenter, at which NW explosion can produce RCI. Mathematical formalism comprises a set of equations for the reciprocal assessment of a distance-effect for radiation dose (separately for neutrons and gamma-rays), thermal wave and blast shock wave depending on the NW type, detonation yield and altitude, environmental conditions (i.e. season) and shielding factors. The model's capabilities were demonstrated using an example of the RCI grade causing a profound operational performance decrement of military personnel in two marginal scenarios: Troops deployed in an open area or a tank crew.

RESULTS

A remarkable difference in the expected radial zones of possible RCI occurrence was found between the actions of a 'historical' atomic bomb, thermonuclear weapons, and low-yield neutron munitions, also with a noticeable impact of the season factor (summer/winter). For a tank crew the clinically manageable RCI are possible only in very high yield explosion scenarios, while the damage caused by radiation alone possess much higher risk.

CONCLUSIONS

Suggested formalism may provide guidance for a preliminary planning of countermeasures, targeting of radiation reconnaissance, and clarification of triage results in a broad range of radiological scenarios based on NW detonation. Further improvement of the model is possible by considering neutrons' and gamma-rays' relative biological efficacy, possible shielding factors, and a synergetic effect of NW's destructive forces.